Mobile IP mobile router

ABSTRACT

Methods and apparatus for implementing a Mobile IP mobile router are provided. In accordance with one aspect, the Home Agent receives a registration request packet. The registration request packet may include a care-of address for the mobile router. Networks associated with the mobile router are then identified. The Home Agent then updates a routing table to associate the identified networks with the care-of address. In addition, the Home Agent updates a mobility binding table with the care-of address for the mobile router. In accordance with another aspect, routing information is exchanged between the Home Agent and the mobile router. A routing table associated with at least one of the Home Agent and the mobile router is then updated as appropriate to include the exchanged routing information.

RELATED APPLICATIONS

This application is a continuation and claims priority of applicationSer. No. 09/227,396, entitled “Mobile IP Mobile Router,” naming Kent K.Leung as inventor, filed on Jan. 8, 1999, now U.S. Pat. No. 6,636,498which is incorporated herein by reference for all purposes.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to Mobile IP network technology. Moreparticularly, the present invention relates to a Mobile IP mobilerouter.

2. Description of the Related Art

Mobile IP is a protocol which allows laptop computers or other mobilecomputer units (referred to as “Mobile Nodes” herein) to roam betweenvarious sub-networks at various locations—while maintaining internetand/or WAN connectivity. Without Mobile IP or related protocol, a MobileNode would be unable to stay connected while roaming through varioussub-networks. This is because the IP address required for any node tocommunicate over the internet is location specific. Each IP address hasa field that specifies the particular sub-network on which the noderesides. If a user desires to take a computer which is normally attachedto one node and roam with it so that it passes through differentsub-networks, it cannot use its home base IP address. As a result, abusiness person traveling across the country cannot merely roam with hisor her computer across geographically disparate network segments orwireless nodes while remaining connected over the internet. This is notan acceptable state-of-affairs in the age of portable computationaldevices.

To address this problem, the Mobile IP protocol has been developed andimplemented. An implementation of Mobile IP is described in RFC 2002 ofthe Network Working Group, C. Perkins, Ed., October 1996. Mobile IP isalso described in the text “Mobile IP Unplugged” by J. Solomon, PrenticeHall. Both of these references are incorporated herein by reference intheir entireties and for all purposes.

The Mobile IP process and environment are illustrated in FIG. 1A. Asshown there, a Mobile IP environment 2 includes the internet (or a WAN)4 over which a Mobile Node 6 can communicate remotely via mediation by aHome Agent 8 and a Foreign Agent 10. Typically, the Home Agent andForeign Agent are routers or other network connection devices performingappropriate Mobile IP functions as implemented by software, hardware,and/or firmware. A particular Mobile Node (e.g., a laptop computer)plugged into its home network segment connects with the internet throughits designated Home Agent. When the Mobile Node roams, it communicatesvia the internet through an available Foreign Agent. Presumably, thereare many Foreign Agents available at geographically disparate locationsto allow wide spread internet connection via the Mobile IP protocol.Note that it is also possible for the Mobile Node to register directlywith its Home Agent.

As shown in FIG. 1A, Mobile Node 6 normally resides on (or is “basedat”) a network segment 12 which allows its network entities tocommunicate over the internet 4 through Home Agent 8 (an appropriatelyconfigured router denoted R2). Note that Home Agent 8 need not directlyconnect to the internet. For example, as shown in FIG. 1A, it may beconnected through another router (a router R1 in this case). Router R1may, in turn, connect one or more other routers (e.g., a router R3) withthe internet.

Now, suppose that Mobile Node 6 is removed from its home base networksegment 12 and roams to a remote network segment 14. Network segment 14may include various other nodes such as a PC 16. The nodes on networksegment 14 communicate with the internet through a router which doublesas Foreign Agent 10. Mobile Node 6 may identify Foreign Agent 10 throughvarious solicitations and advertisements which form part of the MobileIP protocol. When Mobile Node 6 engages with network segment 14, ForeignAgent 10 relays a registration request to Home Agent 8 (as indicated bythe dotted line “Registration”). The Home and Foreign Agents may thennegotiate the conditions of the Mobile Node's attachment to ForeignAgent 10. For example, the attachment may be limited to a period oftime, such as two hours. When the negotiation is successfully completed,Home Agent 8 updates an internal “mobility binding table” whichspecifies the care-of address (e.g., a collocated care-of address or theForeign Agent's IP address) in association with the identity of MobileNode 6. Further, the Foreign Agent 10 updates an internal “visitortable” which specifies the Mobile Node address, Home Agent address, etc.In effect, the Mobile Node's home base IP address (associated withsegment 12) has been shifted to the Foreign Agent's IP address(associated with segment 14).

Now, suppose that Mobile Node 6 wishes to send a message to acorresponding node 18 from its new location. A message from the MobileNode is then packetized and forwarded through Foreign Agent 10 over theinternet 4 and to corresponding node 18 (as indicated by the dotted line“packet from MN”) according to a standard internet protocol. Ifcorresponding node 18 wishes to send a message to Mobile Node—whether inreply to a message from the Mobile Node or for any other reason—itaddresses that message to the IP address of Mobile Node 6 on sub-network12. The packets of that message are then forwarded over the internet 4and to router R1 and ultimately to Home Agent 8 as indicated by thedotted line (“packet to MN(1)”). From its mobility binding table, HomeAgent 8 recognizes that Mobile Node 6 is no longer attached to networksegment 12. It then encapsulates the packets from corresponding node 18(which are addressed to Mobile Node 6 on network segment 12) accordingto a Mobile IP protocol and forwards these encapsulated packets to a“care of” address for Mobile Node 6 as shown by the dotted line (“packetto MN(2)”). The care-of address may be, for example, the IP address ofForeign Agent 10. Foreign Agent 10 then strips the encapsulation andforwards the message to Mobile Node 6 on sub-network 14. The packetforwarding mechanism implemented by the Home and Foreign Agents is oftenreferred to as “tunneling.”

In addition to providing connectivity to a mobile node, it may bedesirable to provide for the mobility of one or more networks movingtogether, such as on an airplane or a ship. RFC 2002 section 4.5discusses the possibility of implementing mobile routers.

In one approach suggested in RFC 2002 section 4.5, a Home Agent isconfigured to have a permanent registration for each fixed node. FIG. 1Bis a diagram of a Mobile IP mobile router and associated environment inwhich a Home Agent is configured to have a permanent registration foreach fixed node. As shown, a mobile router 20 may support multiple nodes22, 24, 26 which may be fixed with respect to the mobile router 20. Inorder to receive communication from a corresponding node 28, messagesmust be routed to the appropriate fixed node 22, 24, or 26. As the RFCsuggests, a Home Agent 30 may be configured to have a permanentregistration for each fixed node. By way of example, the permanentregistration may indicate the mobile router's address as the care-ofaddress. Thus, a separate mapping table may associate the IP address ofeach of the fixed nodes 22, 24, and 26 with the mobile router 20.However, this is problematic since the mapping table is typicallyconfigured while the mobile router 20 is coupled to the Home Agent 30.In other words, the routing table is static. Suppose a person boards anairplane and wishes to connect a laptop to the airplane's “mobilenetwork” via the mobile router 20. If a new node 32 is added to themobile router 20 after the airplane leaves the airport, the IP addressof this new node may not be added to the mapping table. As a result,communication cannot be received by this new node 32 via the mobilerouter 20. In addition, since the mobile router 20 may accommodatethousands of devices, or nodes, there would potentially be an enormousnumber of entries to store in such a mapping table for these nodes.Moreover, such a mapping table may include entries for multiple mobilerouters. Accordingly, such a mapping table would consume a substantialamount of memory as well as be cumbersome to search.

In another approach suggested in RFC 2002, the mobile router 20 mayadvertise connectivity to the entire “mobile network.” FIG. 1C is adiagram of a Mobile IP mobile router and associated environment in whichthe mobile router advertises 34 connectivity to each node associatedwith the mobile router. The RFC states that this may be performed usingnormal IP routing protocols through a bi-directional tunnel to its HomeAgent 30. However, the RFC provides no implementation details.

In view of the above, it would be desirable to have improved techniquesfor implementing a Mobile IP mobile router.

SUMMARY OF THE INVENTION

Methods and apparatus for providing Mobile IP mobile routerfunctionality are provided. This is accomplished through identifyingnetworks associated with the mobile router which may then be used toupdate the appropriate tables. Thus, the Home Agent does not need toseparately track each node associated with the mobile router.

In accordance with one aspect of the invention, the Home Agent receivesa registration request packet. The registration request packet mayinclude a care-of address for the mobile router. Networks associatedwith the mobile router are then identified. The Home Agent then updatesa routing table to associate the identified networks with the care-ofaddress. In addition, the Home Agent updates a mobility binding tablewith the care-of address for the mobile router.

In accordance with another aspect of the invention, at least one networklinked to the mobile router is listed in an extension appended to theregistration request. Upon receipt of such request, the Home Agentidentifies networks associated with the mobile router from theextension. The Home Agent then updates a routing table to associate thecare-of address with the identified networks and updates a mobilitybinding table with the care-of address. In addition, the Foreign Agentmay update a visitor table with an entry for each of the networks listedon the extension to associate those networks with the mobile router.

In accordance with yet another aspect of the invention, routinginformation is exchanged between the Home Agent and the mobile router. Arouting table associated with at least one of the Home Agent and themobile router is updated as appropriate to include the exchanged routinginformation. By way of example, networks associated with the mobilerouter may be obtained from the exchanged routing information and theappropriate routing tables may be updated to associate the networks withthe care-of address for the mobile router. In addition, the Home Agentupdates its mobility binding table with the care-of address. If thecare-of address is the address of a Foreign Agent, a visitor table maybe updated to associate the networks with the mobile router.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a diagram of a Mobile IP network segment and associatedenvironment.

FIG. 1B is a diagram of a Mobile IP mobile router and associatedenvironment in which a Home Agent is configured to have a permanentregistration for each fixed node that indicates the mobile router'saddress as the care-of address.

FIG. 1C is a diagram of a Mobile IP mobile router and associatedenvironment in which the mobile router advertises connectivity to eachmobile network associated with the mobile router.

FIG. 2A-1 is a diagram illustrating a Mobile IP mobile router andassociated environment in which the mobile router is stationed at theHome Agent.

FIGS. 2A-2 is a diagram illustrating an exemplary mapping table that maybe used by an active Home Agent in accordance with an embodiment of theinvention.

FIGS. 2A-3 is a diagram illustrating an exemplary routing table that maybe used by an active Home Agent when the mobile router is at the HomeAgent in accordance with an embodiment of the invention.

FIGS. 2A-4 is a diagram illustrating a Mobile IP mobile router andassociated environment when the mobile router is roaming according to afirst embodiment of the invention.

FIGS. 2B-1 is a diagram illustrating an exemplary mobility binding tableassociated with a first Foreign Agent that may be used by an active HomeAgent in accordance with an embodiment of the invention.

FIGS. 2B-2 is a diagram illustrating exemplary routing and interfacetables associated with a first Foreign Agent that may be used by anactive Home Agent in accordance with an embodiment of the invention.

FIGS. 2B-3 is a diagram illustrating exemplary routing and interfacetables associated with a collocated care-of address that may be used byan active Home Agent in accordance with an embodiment of the invention.

FIGS. 2C-1 is a diagram illustrating an exemplary mobility binding tableassociated with a second Foreign Agent that may be used by an activeHome Agent in accordance with an embodiment of the invention.

FIGS. 2C-2 is a diagram illustrating exemplary routing and interfacetables associated with a second Foreign Agent that may be used by anactive Home Agent in accordance with an embodiment of the invention.

FIG. 3A is a process flow diagram illustrating the steps performed by aHome Agent and a Foreign Agent to provide mobile router functionality inaccordance with the first embodiment of the invention.

FIG. 3B is a diagram illustrating packet header encapsulation typicallyperformed when a packet is sent to a mobile node from a correspondingnode.

FIG. 3C is a diagram illustrating packet header encapsulation duringrecursive tunneling that may occur during an embodiment of theinvention.

FIG. 4 is a diagram illustrating a Mobile IP mobile router andassociated environment in which a Home Agent may install routes tomobile networks specified in a registration request according to asecond embodiment of the invention.

FIG. 5 is a diagram illustrating a registration request having anextension that may be sent by a Mobile IP mobile router in accordancewith an embodiment of the invention.

FIG. 6A is a diagram illustrating a conventional visitor table that maybe used by an active Foreign Agent.

FIG. 6B is a diagram illustrating a visitor table that may be used by anactive Foreign Agent in accordance with an embodiment of the invention.

FIG. 7 is a process flow diagram illustrating the steps performed by aHome Agent and a Foreign Agent to provide mobile router functionality inaccordance with the second embodiment of the invention.

FIG. 8 is a diagram illustrating a Mobile IP mobile router andassociated environment in which a Home Agent may install routes tomobile networks via IP routing protocols in accordance with a thirdembodiment of the invention.

FIG. 9 is a process flow diagram illustrating the steps performed by aHome Agent and a Foreign Agent to provide mobile router functionality inaccordance with the third embodiment of the invention.

FIG. 10 is a block diagram of a network device that may be configured toimplement aspects of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, numerous specific details are set forth inorder to provide a thorough understanding of the present invention. Itwill be apparent, however, to one skilled in the art, that the presentinvention may be practiced without some or all of these specificdetails. In other instances, well known process steps have not beendescribed in detail in order not to unnecessarily obscure the presentinvention.

An invention is described herein which provides Mobile IP mobile routerfunctionality. When a mobile router moves to a new geographicallocation, it constructs a registration request and registers with itsHome Agent via a care-of address. Upon receipt of the registrationrequest, the Home Agent verifies authentication of the registrationrequest packet and updates the appropriate tables. Registration isperformed once for the mobile router. From the registration packet andsometimes from information easily accessible to the Home Agent, the Homeagent registers the care-of address for the network(s) serviced by themobile router. This eliminates the necessity for the Home Agent toseparately track each node associated with the mobile router.

In accordance with one embodiment, the Home Agent receives aregistration request when the mobile router moves to a new location. Itthen identifies networks associated with the mobile router from a localstatic mapping table. The Home Agent then updates its routing table toassociate the care-of address with the networks. In addition, the HomeAgent updates a mobility binding table with the care-of address for themobile router.

In accordance with another embodiment, networks associated with themobile router are listed in an extension appended to the registrationrequest. Upon receipt of such request, the Home Agent then updates itsrouting table to associate the care-of address with the networks andupdates its mobility binding table with the care-of address, asdescribed above. In addition, the Foreign Agent updates a visitor tablewith an entry for each of the networks listed on the extension toassociate those networks with the mobile router. The foreign agent willthus recognize the destination of packets addressed to nodes on themobile router's networks.

In accordance with yet another embodiment, routing information isexchanged between the Home Agent and the mobile router via an IP routingprotocol via a bi-directional tunnel. A routing table associated with atleast one of the Home Agent and the mobile router is updated asappropriate for the particular routing protocol. Networks associatedwith the mobile router are obtained from the exchanged routinginformation and the appropriate routing tables are updated to associatethe networks with the care-of address. In addition, the Home Agentupdates its mobility binding table with the care-of address. If thecare-of address is the address of a Foreign Agent, a visitor table maybe updated to associate the networks with the mobile router.

FIGS. 2A-1 is a diagram illustrating a Mobile IP mobile router andassociated environment in which the mobile router is stationed at theHome Agent. As shown, a Mobile IP environment 202 includes the internet(or a WAN) 204 over which a node such as “node 1” 217 connected tomobile router 206 can communicate remotely with a corresponding node 208via mediation by a Home Agent 210 and a Foreign Agent. By way ofexample, the Home Agent 210 and the Foreign Agent may be network devicessuch as routers or hosts having Mobile IP capabilities. The mobilerouter may include Mobile IP software. The mobile router 206 may provideconnectivity to multiple networks, many or all of which may roam withmobile router 206. As shown, the mobile router 206 provides connectivityto a first mobile network, “network 10” 216, and a second network,“network 11” 218. Although only one network, “network 10” 216, in thefollowing examples is mobile, other networks such as the second network,“network 11” 218, may be mobile networks.

Each network and network device is assigned a unique IP address. IPaddresses typically include a network-prefix portion and a host portion.By way of example, the network-prefix may consist of the leftmost 8 bitsand the host portion may consist of the rightmost 24 bits. Exemplary IPaddresses are provided, as shown. The Home Agent 210 has an IP address40.0.0.1, the mobile router has an IP address 40.0.0.4, the firstnetwork 216 has an IP address 10.0.0.0/8 and the second network has anIP address 11.0.0.0/8. A 32-bit mask may be used to specify the entireIP address (e.g., 40.0.0.4/32). Alternatively, a mask may be used toexclude the rightmost 24 bits of the network addresses that areassociated with the mobile router supported networks, as shown. In thismanner, the network portion of the IP addresses may be used in routingdecisions to route packets to nodes 217 and 219, identified by IPaddresses 10.0.0.1 and 11.0.0.2, respectively.

A Home Agent may be configured to include a mapping of mobile networksassociated with the mobile router. For this purpose, a mapping table maybe used to associate the mobile router with one or more networks. FIGS.2A-2 is a diagram illustrating an exemplary mapping table that may beused by an active Home Agent in accordance with an embodiment of theinvention. As shown, mapping table 268 associates each mobile router 270with associated mobile networks 272. As shown, the mobile router 274 maybe designated by its IP address, 40.0.0.4. The mobile router 274 isassociated with the first network 276, network 10, which may bedesignated its IP address, 10.0.0.0/8. In one embodiment, mapping table268 is static and may be updated by an administrator.

FIGS. 2A-3 is a diagram illustrating an exemplary routing table that maybe used by an active Home Agent when the mobile router is stationed atthe Home Agent in accordance with an embodiment of the invention.Routing table 278 associated with the Home Agent includes an entry forone or more networks that are coupled to the mobile router. As shown,each entry in the routing table 278 may include a care-of addressassociated with the networks that are coupled to the mobile router. Asshown, each entry may include a network IP address 280, a next hoprouter IP address to the care-of address for the network 282, and aninterface 284. As shown, a first entry 286 may include an IP address forthe first network 288, 10.0.0.0/8, the IP address of the mobile router290, 40.0.0.4, and an interface 292, IntA. Similarly, a second entry 294may include an IP address for the second network 296, 11.0.0.0/8, the IPaddress of the mobile router 298, 40.0.0.4, and an interface 300, IntA.

FIGS. 2A-4 is a diagram illustrating a Mobile IP mobile router andassociated environment when the mobile router is roaming according to afirst embodiment of the invention. As shown, the mobile router may belinked to a first available Foreign Agent 212. As the mobile routerroams, it may then communicate through a second available Foreign Agent214 at another geographical location. As described above, the mobilerouter 206 may provide connectivity to multiple networks, many or all ofwhich may roam with mobile router 206. Although only one network,“network 10” 216, is shown to be mobile, other networks may be mobilenetworks. Exemplary IP addresses are provided, as shown. The Home Agent210 has an IP address 40.0.0.1, the first Foreign Agent 212 has an IPaddress 20.0.0.2, the second Foreign Agent 214 has an IP address31.0.0.3, the mobile router has an IP address 40.0.0.4, the firstnetwork 216 has an IP address 10.0.0.0/8 and the second network has anIP address 11.0.0.0/8.

In order to provide for connectivity to multiple networks, the HomeAgent may have a mobility binding table, a routing table, and a mobilerouter/network mapping table available for its use. The mapping tablemay be used to associate the mobile router with one or more networks.Since the networks associated with the mobile router are typicallyconfigured at the time that the mobile router is connected to the HomeAgent, the mapping table may be static during registration of the mobilerouter. The routing table and the mobility binding table may then beused to associate a care-of address with the mobile router and thenetworks. Specifically, the routing table associates each one of thenetworks with a care-of address through a tunnel interface to the mobilerouter. Similarly, the mobility binding table associates the mobilerouter with the care-of address.

Exemplary mobility binding, routing tables, and interface tableassociated with a first Foreign Agent that may be used by an active HomeAgent in accordance with an embodiment of the invention are illustratedin FIGS. 2B-1, 2B-2, and 2B-3. As shown in FIGS. 2B-1, mobility bindingtable 220 associates mobile router 222 with care-of address 224. Thecare-of address 224 may be a foreign agent address as well as acollocated care-of address. In this example, the care-of address 224 isthe IP address of the first Foreign Agent, 20.0.0.2. As shown, themobile router 222 may be designated by its IP address, 40.0.0.4. Inaddition, the mobility binding table 220 may include a tunnel interface(not shown to simplify illustration). Moreover, the mobility bindingtable 220 may include care-of address associations for additional mobilerouters (and other mobile nodes) based with the same Home Agent. Suchadditional mobile routers/nodes may be linked to the first Foreign Agentor any other Foreign Agent that has registered a Mobile IP connection.

In addition, a routing table is used to route packets to each mobilerouter supported network. Routing tables typically include a targetfield, a next hop field, and an interface field. When a node has an IPpacket to forward, it searches its routing table for an entry whosetarget field matches the IP destination address in the packet header ofthe packet being forwarded. If it finds a matching entry, the nodeforwards the packet to the node identified by the next hop field in thatentry via the link specified in the interface field of that entry.

FIGS. 2B-2 is a diagram illustrating exemplary routing and interfacetables associated with a first Foreign Agent that may be used by anactive Home Agent in accordance with an embodiment of the invention. Asshown in FIGS. 2B-2, routing table 226 containing entries for the firstForeign Agent and associated with the Home Agent includes an entry foreach of the mobile networks that are coupled to the mobile router. Eachentry in the routing table 226 may include a care-of address associatedwith the one or more networks. As shown, a first entry 228 may includean IP address for the first network 230, 10.0.0.0/8, IP address of thenext hop router to the care-of address for the first network 232,40.0.0.4, and an interface 234, tunnel 0. Thus, the interface willprovide an identifier of the tunnel created during registration. Asecond entry 236 may include the router IP address 238, 40.0.0.4, a nexthop router IP address to the care-of address 240, 20.0.0.2, and aninterface 242, tunnel 1. Because routing table 226 may contain IPaddresses and care-of addresses for the one or more networks associatedwith the mobile router, packets addressed to nodes on these networks areidentified by the Home Agent and tunneled to the care-of addresses.

Interface table 244 may include a first entry 246 providing the tunnelname of the interface 248, tunnel 0, the source address of tunnel 0 250,40.0.0.1, and the destination address of tunnel 0 252, 40.0.0.4.Similarly, a second entry 254 may provide the tunnel name of theinterface 256, tunnel 1, the source address of tunnel 1 258, 40.0.0.1,and the destination address of tunnel 1 260, 20.0.0.2. Thus, the sourceaddress of the tunnels is the Home Agent interface 40.0.0.1.

FIGS. 2B-3 is a diagram illustrating exemplary routing and interfacetables associated with a collocated care-of address that may be used byan active Home Agent in accordance with an embodiment of the invention.As shown in FIGS. 2B-3, routing table 262 may include a care-of addressassociated with one or more networks. As shown, an entry 264 may includean IP address for the first network 266, 10.0.0.0/8, a next hop routerIP address to the care-of address for the first network 268, and aninterface 270, tunnel 0. Thus, the interface will provide an identifierof the tunnel created during registration.

In addition to a routing table, an interface table may be provided.Interface table 272 may include an entry 274 providing the tunnel nameof the interface 276, tunnel 0, the source address of tunnel 0 278,40.0.0.1, and the destination address of tunnel 0 280, the care-ofaddress.

FIGS. 2B-1 through 2C-2 may be snapshots of the routing, mobility, andinterface tables taken at different times (as the mobile router roamsbetween Foreign Agents). FIGS. 2C-1 is a diagram illustrating anexemplary mobility binding table associated with a second Foreign Agentthat may be used by an active Home Agent in accordance with anembodiment of the invention. As shown, mobility binding table 281associates mobile router 282 with its care-of address 283. In thisexample, the care-of address 283 is the IP address of the second ForeignAgent, 31.0.0.3. In addition, the mobile router 282 may be designated byits IP address, 40.0.0.4. Moreover, the mobility binding table 244 mayinclude care-of address associations for one or more mobile routers thatare linked to the second Foreign Agent.

FIGS. 2C-2 is a diagram illustrating exemplary routing and interfacetables associated with a second Foreign Agent that may be used by anactive Home Agent in accordance with an embodiment of the invention. Asshown in FIGS. 2B-2, routing table 284 containing entries for the secondForeign Agent and associated with the Home Agent includes an entry foreach of the one or more networks that are coupled to the mobile router.Each entry in the routing table 284 may include a care-of addressassociated with the one or more networks. As shown, a first entry 285may include an IP address for the first network 286, 10.0.0.0/8, a nexthop router IP address to the care-of address for the first network 287,40.0.0.4, and an interface 288, tunnel 2. A second entry 289 may includethe router IP address 290, 40.0.0.4/32, a next hop router IP address tothe care-of address 291, 31.0.0.3, and an interface 292, tunnel 3. Thus,the one or more networks may be designated by a corresponding IPaddress.

Interface table 293 may include a first entry providing the tunnel nameof the interface 294, tunnel 2, the source address of tunnel 2 295,40.0.0.1, and the destination address of tunnel 2 296, 40.0.0.4.Similarly, a second entry may provide the tunnel name of the interface297, tunnel 3, the source address of tunnel 3 298, 40.0.0.1, and thedestination address of tunnel 3 299, 31.0.0.3. Thus, the source addressof the tunnels is the Home Agent interface 40.0.0.1.

FIG. 3A is a process flow diagram illustrating the steps performed by aHome Agent and a Foreign Agent to provide mobile router functionality inaccordance with the first embodiment of the invention. As shown, theregistration process begins at step 302 and at step 304 the process flowdiverges depending upon whether the mobile router connects through aforeign agent. If there is no foreign agent, a collocated care-ofaddress is obtained at step 306. A collocated care-of address is an IPaddress temporarily assigned to an interface of the mobile node itself,or mobile router in this instance. Thus, the care-of address may be anIP address associated with the mobile router. In other words, throughthe use of a collocated care-of address, packets may be tunneleddirectly to the mobile router.

Once the care-of address has been obtained, a registration request iscomposed and sent via the care-of address. If there is a foreign agent,the registration request is composed and sent via the foreign agentcare-of address at step 308. Alternatively, after the collocated care-ofaddress is obtained at step 306, the registration request is composedand sent via the collocated care-of address at step 310.

Once the registration request is sent (via Foreign Agent care-of addressor collocated care-of address), it is received by the Home Agent at step312. The registration request comprises a registration request packetthat includes the care-of address for the mobile router. Next, at step314, it is determined whether the registration is authenticated by theHome Agent, as provided by RFC 2002 for example. At step 316, if theregistration is not authenticated, the mobile router is not registeredwith the Home Agent and the process is complete as indicated at step318.

If the registration is authenticated, registration is completed by theHome Agent in steps 320 through 324. At step 320, networks associatedwith the mobile router are identified. According to the firstembodiment, the networks associated with the mobile router are obtainedfrom a mobile router/network mapping table such as that illustrated inFIGS. 2A-2. Tunnel interfaces to reach the mobile router may then becreated at step 321. At step 322, a routing table such as thatillustrated in FIGS. 2B-2 and FIGS. 2C-2 is updated to associate theidentified networks with the care-of address (obtained from theregistration request packet). A mobility table such as that illustratedin FIGS. 2B-1 and 2C-1 is similarly updated to include the care-ofaddress for the mobile router at step 324. As described above, thecare-of address may be an IP address of a Foreign Agent or a collocatedcare-of address. The process flow then ends at step 318.

The first embodiment provides significant advantages over the mobilerouter implementations suggested by the RFC. For instance, since therouting table contains networks associated with the mobile router ratherthan all nodes, this implementation is scalable for many fixed nodesassociated with these networks. In addition, the registration requestpacket format need not be altered.

Although the first embodiment provides certain advantages, thisembodiment may require recursive tunneling if used with a Foreign Agent,as will be described with reference to FIG. 3B and FIG. 3C. Typically,when a packet is sent to a mobile node from a corresponding node, thepacket is encapsulated twice. FIG. 3B is a diagram illustrating suchtwo-level encapsulation. The packet is encapsulated in a first step whenthe packet is sent from the corresponding node to the Home Agent and ina second step when it is forwarded from the Home Agent to the care-ofaddress (e.g., Foreign Agent). The first step typically involvesapplying the standard header used for most all IP packets. As shown, inthe first encapsulation step, a packet header 338 having a destinationfield 340 specifying the node N and a source field 342 specifying thecorresponding node CN is created. The packet is then sent from thecorresponding node CN to the Home Agent. When the packet is received bythe Home Agent, a second encapsulation step is performed. The secondstep involves applying the basic Mobile IP header to the packet (asspecified in RFC 2002). As shown, a second packet header 344 having adestination field 346 specifying the care-of address for the mobile nodeand a source field 348 specifying the Home Agent is formed. Thus, thesecond level of encapsulation serves to direct (tunnel) the packet fromthe Home Agent to the Foreign Agent. When the Foreign Agent receives thetunneled packet, it strips off the second layer of encapsulation andforwards the packet to the address provided in the first level ofencapsulation. To accomplish this, the Foreign Agent may consult itsvisitor table, which lists the addresses of all Mobile IP nodes that itis now servicing.

In order to implement a mobile router, an extra layer of encapsulationis required from the Home Agent to the mobile router. In the two-levelencapsulation just described, the Foreign Agent will not forward thepacket destined to the mobile network to the mobile router. Duringregistration, the Foreign Agent received a registration request packetfrom the mobile router. It then updates its visitors table to identifythe mobile router. Because the registration request did not list theroaming nodes (only the roaming router), the visitors table did not listthe network nodes roaming with the mobile router. Therefore, a thirdlayer of encapsulation is required, to implement “recursive tunneling,”so that the Foreign Agent can forward the packets destined to thenetwork nodes to the mobile router.

FIG. 3C is a diagram illustrating a packet header encapsulationprocedure that may be performed during recursive tunneling. Duringrecursive tunneling, when a packet is forwarded from a correspondingnode (CN) to a node (N) linked to the mobile router (MR), there arethree encapsulation steps that are applied. In a first encapsulationstep, a packet header 320 having a destination field 322 specifying thenode N and a source field 324 specifying the corresponding node CN iscreated. The packet is then sent from the corresponding node CN to theHome Agent. When the packet is received by the Home Agent, twoadditional levels of encapsulation are provided prior to forwarding ofthe packet to the mobile router. During a second encapsulation step, asecond packet header 326 having a destination field 328 specifying themobile router MR and a source field 330 specifying the Home Agent isformed. In a third encapsulation step, a third packet header 332 havinga destination field 334 specifying a care-of address and a source field336 specifying the Home Agent is created. Thus, when the packet isforwarded from the Home Agent to the care-of address, an extraencapsulation step is applied.

As described above, registration is accomplished in the first embodimentthrough the use of a mapping table which contains mobile routersupported networks. FIG. 4 is a diagram illustrating a Mobile IP mobilerouter and associated environment in which a Home Agent may installroutes to mobile networks specified in a registration request accordingto a second embodiment of the invention. The environment shown in FIG. 4is substantially the same as that of FIGS. 2A-4. However, in the secondembodiment, the registration request 402 composed and sent by the mobilerouter contains information which will be used to install routes to the“mobile networks” associated with the mobile router. More particularly,the registration request 402 includes an extension which lists networksassociated with the mobile router. This may eliminate the need forrecursive tunneling.

The RFC provides a format for a registration request packet as well asoptional extensions. FIG. 5 is a diagram illustrating a registrationrequest having an extension that may be sent by a Mobile IP mobilerouter in accordance with an embodiment of the invention. As shown, aregistration request packet 502 includes an IP Header 504 as defined inRFC 791. As is well-known in the field, the IP Header 504 includes aversion field 506 which specifies which versions of the InternetProtocol are represented in the registration request packet 502. AnInternet Header Length (IHL) field 508 provides the length of the IPheader 504. In addition, a Type of Service field 510 is used to specifyhow the registration request packet 502 is to be handled in networkswhich offer various service qualities. A Total Length field 512 givesthe length of the registration request packet in bytes. In addition, anIdentification field 514 is a unique value chosen by the sender to allowa recipient to reassemble a packet that had been separated intofragments. A Flags field 516 and a Fragment Offset field 518 are both toseparate an IP registration request packet into fragments to traversenetworks that are unable to handle large IP packets. A Time to Livefield 520 is used to limit the number of times an individual IP packetmay be forwarded. A Protocol field 522 is used by the IP layer todetermine which higher layer protocol created the “payload,” or datapassed down from the higher layer protocol, within the IP packet. AHeader Checksum field 524 is used by a receiving node to verify thatthere was no error in transmission of the IP-header portion of thepacket. In addition, the IP Header 504 includes a source address 526 anda destination address 528 of the registration request packet 502.

A UDP Header field 530 is provided by RFC 768. As is well-known in thefield, the UDP Header field 530 includes a Source Port field 532, whichis selected by the mobile node sending the registration request packet502. In addition, a mobile node sets Destination Port field 534 to 434,the value reserved for Mobile IP registration messages. UDP Length field536 provides the size of the UDP Payload (i.e., the Mobile IP fields)measured in bytes. In addition, a Checksum field 538 permits a receivingnode to determine if an error occurred in transmission.

The registration request packet 502 further includes a Fixed-LengthPortion 540 of the Registration Request which includes the Mobile IPFields as provided in RFC 2002. As shown, the Fixed-Length Portion 540includes multiple fields. A Type field 542 identifies the message aseither a Registration Request or a Registration Reply. In addition, themobile node sets an S bit 544 to 1 to ask that its home agent create ordelete a binding for the specified care-of address without affecting anyother existing bindings.

B, D, M, G, and V bits provide information required for routing of theregistration request packet 502. A B bit 546 is set to 1 by a mobilenode to request that the home agent provide it a copy of broadcastpackets that occur on the home link. A D bit 548 informs the home agentwhich entity is performing decapsulation. The D bit 548 is set to 1 fora collocated care-of address and is set to 0 for a foreign agent care-ofaddress. An M bit 550 and a G bit 552 request that the home agent useminimal encapsulation [RFC 2004] or generic routing encapsulation [RFC1701] respectively, instead of IP in IP encapsulation [RFC 2003] fortunneling. A V bit 554 is set to 1 if the mobile node and foreign agentcan support Van Jacobson Header Compression [RFC 1144] across theforeign link. In addition, an rsv field 556 may be reserved for futureuse.

The remaining fields provide information that may be used duringregistration of the mobile node. The mobile node sets lifetime field 558to the number of seconds it would like its registration to last beforeit expires. In addition, a Mobile Node's Home Address 560 and Home AgentAddress 562 are specified. Care-of Address field 564 is set to thespecific care-of address being registered or deregistered by the mobilenode. In addition, an Identification field 566 is chosen to be uniquefor each attempted registration. The Identification field 566 permitsthe mobile node to match Registration Requests with the correspondingReplies. This prevents an outsider from saving a copy of theRegistration Request and resending it at a later time.

Each Registration Request message is required to contain a Mobile-HomeAuthentication Extension [RFC 2002] 542 to prove that the message wassent by the node that claims to have sent it. In addition, the RFCprovides for optional extensions. However, the RFC does not suggestimplementation details for these optional extensions.

According to the second embodiment, the Mobile IP registration requestpacket includes an extension 544 that specifies at least one networklinked to a mobile router. As shown in FIG. 5, a first network 546,network 10, may be specified by its IP address 548 and an associatednetwork status indicator 550. Similarly, a second network 552, network11, may be specified by its IP address 554 and an associated networkstatus indicator 556. Each network status indicator 550 and 556specifies a first state when the corresponding network is up, and asecond state when the network is down.

In addition, the Foreign Agent may map connectivity to the mobilenetworks through the mobile router. This may be accomplished through theuse of a visitor table. FIG. 6A is a diagram illustrating a conventionalvisitor table that may be used by an active Foreign Agent. As shown,visitor table 602 associates mobile node 604 having an IP address 606(e.g., 10.0.0.1/32) with Home Agent 608 having an IP address 610 (e.g.,40.0.0.1) and a corresponding interface 612. Therefore, each mobile nodeis typically stored in the visitor table.

Rather than storing an entry for each mobile node in the visitor table,it would be preferable to provide entries only for the networksassociated with the mobile router. Packets addressed to nodes on suchnetworks will have addresses indicating the associated networks. Thus,such packets can be forwarded to the appropriate networks.

FIG. 6B is a diagram illustrating a visitor table that may be used by anactive Foreign Agent in accordance with an embodiment of the invention.Visitor table 614 includes an entry for one or more networks that arecoupled to a mobile router such that the mobile router is associatedwith the one or more networks. As shown in FIG. 6B, a first entry 616may include a first network 618, Network 10, designated by its IPaddress 620, 10.0.0.0/8, which is associated with mobile router 622,designated by its IP address 624, 40.0.0.4, and an interface 626.Similarly, a second entry 628 may include a second network 630, Network11, designated by its IP address 632, 11.0.0.0/8, which is associatedwith mobile router 634, designated by its IP address 636, 40.0.0.4, andan interface 638. Therefore, in this example, both the networks 618, 630are associated with the mobile router having the IP address 40.0.0.4.Accordingly, since visitor table entries are associated with networksrather than mobile nodes, the number of entries and memory spacerequired for the visitor table remains small.

Through the use of the registration request packet extension, theappropriate tables may be updated to remove networks that arenon-functional. FIG. 7 is a process flow diagram illustrating the stepsperformed by a Home Agent and a Foreign Agent to provide mobile routerfunctionality in accordance with the second embodiment of the invention.As shown, a registration process begins at step 702 and at step 704 theprocess flow diverges depending upon whether there is a foreign agent.If there is no foreign agent, a collocated care-of address is obtainedat step 706.

Once the care-of address has been obtained, a registration request iscomposed and sent via the care-of address. If there is a foreign agent,the registration request is composed and sent via the foreign agentcare-of address at step 708. Alternatively, after the collocated care-ofaddress is obtained at step 706, the registration request is composedand sent via the collocated care-of address at step 710. Note that ineither approach, composing the registration request includes creatingand appending an extension listing all networks currently handled by themobile router.

The Home Agent receives the registration request at step 712. Theregistration request comprises a registration request packet thatincludes the care-of address associated with the mobile router sendingthe registration request packet and an extension specifying at least onenetwork linked to the mobile router. Next, at step 714, it is determinedwhether the registration is authenticated by the Home Agent as providedby RFC 2002. At step 716, if the registration is not authenticated, themobile router is not registered with the Home Agent and the process iscomplete as indicated at step 718.

If the registration is authenticated, registration is completed in steps720 through 724. At step 720, networks associated with the mobile routerare identified from the extension of the registration request packet. Byway of example, each network specified in the extension that has astatus indicating that the network is in an active state may beidentified. Next, at step 722, a visitor table associated with theForeign Agent such as that illustrated in FIG. 6B may be updated withentries for selected networks that are specified in the extension. Inthis manner, the selected networks are associated with the mobilerouter, from the Foreign Agent's perspective. At step 724, the HomeAgent updates a routing table such as that illustrated in FIGS. 2B-2 and2B-3 and FIGS. 2C-2 and 2C-3 to associate the identified networks withthe care-of address. Next, at step 726, the Home Agent updates amobility binding table such as that illustrated in FIGS. 2B-1 and 2C-1to associate the care-of address with the mobile router. In this manner,only networks that are functional may be stored in the visitor table andthe routing tables. Accordingly, the visitor and routing tables storeminimal information, reducing the memory required to store the tables aswell as the time required to search the tables.

The second implementation provides certain and additional advantagesover the first implementation. Through the use of an extension whichsupplies networks (as opposed to nodes) associated with the mobilerouter, this implementation is scalable for many fixed nodes associatedwith the mobile router. Moreover, this implementation is dynamic sincenetworks which are non-functional may be removed from the appropriatetables. In addition, a static mapping table such as that used in thefirst implementation is not required, yielding a dynamic registrationsystem. As a result, tables may be updated without downtime. Forexample, the Home Agent can handle changes in the networks associatedwith the mobile router, without requiring an administrator toreconfigure the mapping table.

One significant advantage is that recursive tunneling is not requiredsince the registration request packet extension contains the networksassociated with the mobile node. Rather than use recursive tunneling,the Foreign Agent routes packets to the networks associated with themobile router via the mobile router. As a result, the Foreign Agent mayassociate the mobile router with the networks and therefore ascertainthat the destination of a packet is the mobile router. As describedabove, this may be accomplished through the creation of one or moreentries in a visitor table. The Foreign Agent therefore has access tothe networks associated with the mobile router. Thus, when a packet islater received by the Foreign Agent, the packet may be de-capsulated andforwarded using the visitor table.

Although there are various advantages to the use of an extension thatspecifies mobile networks, this approach could require furtherstandardization beyond that specified in RFC 2002. The RFC does providefor extensions, as described above. However, standardization wouldrequire that such an extension be both publicized and adopted. Moreover,the mobile networks should have public IP addresses to be uniquelyidentified by a Foreign Agent.

Rather than requiring standardization of a registration request packetextension, it would be desirable if standard IP routing protocols couldbe used to update router information that changes during roaming inMobile IP. FIG. 8 is a diagram illustrating a Mobile IP mobile routerand associated environment in which a Home Agent may install routes tomobile networks via IP routing protocols in accordance with a thirdembodiment of the invention. The environment shown in FIG. 8 issubstantially the same as that of FIGS. 2A-4. However, in the thirdembodiment, routing information 802 is exchanged between the Home Agentand the Foreign Agent via normal IP routing protocols. This exchangedrouting information may then be used to update the appropriate tables.

In the third embodiment, the Home Agent installs routes to networksassociated with the mobile router which are received via an IP routingprotocol. There are two modes of operation for the third embodiment. Inboth modes, the mobile router registers with the Home Agent via acare-of address. In the first mode, the care-of address is the IPaddress of a Foreign Agent. However, in the second mode, the care-ofaddress is a collocated care-of address.

FIG. 9 is a process flow diagram illustrating the steps performed by aHome Agent and a Foreign Agent to provide mobile router functionality inaccordance with the third embodiment of the invention. A registrationprocess begins at step 902 and at step 904 the process divergesdepending upon whether there is a foreign agent. If there is no foreignagent, a collocated care-of address is obtained at step 906.

Once the care-of address has been obtained, a registration request iscomposed and sent via the care-of address. If there is a foreign agent,the registration request is composed and sent via the foreign agentcare-of address at step 908. Alternatively, after the collocated care-ofaddress is obtained at step 906, the registration request is composedand sent via the collocated care-of address at step 910.

The Home Agent receives the registration request at step 912. Asdescribed above, the registration request comprises a registrationrequest packet that includes the care-of address for the mobile router.Next, at step 914, it is determined whether the registration isauthenticated by the Home Agent. If the registration is notauthenticated at step 916, the mobile router is not registered with theHome Agent and the process is complete as indicated at step 918.

If the registration is authenticated, registration is completed at theHome Agent in steps 920 through 928. A mobility binding table is updatedat step 920 by the Home Agent to include the care-of address for themobile router. The Home Agent and the mobile router subsequentlyexchange routing information and at least one routing table is updatedto include the exchanged routing information at step 922.

The routing information is exchanged through a bi-directional tunnelbetween the Home Agent and the mobile router. In other words, routinginformation is encapsulated and tunneled from the Home Agent to themobile router and routing information is reverse encapsulated andtunneled from the mobile router to the Home Agent. Such routinginformation may include the networks associated with the mobile router,metrics associated with the networks, and the status of the networks.The Home Agent may then update its routing table using this routinginformation, allowing the Home Agent to forward a packet to the care-ofaddress specified in the routing table.

In accordance with the third embodiment, the routing information may beexchanged via any suitable IP routing protocol (e.g., RoutingInformation Protocol (RIP)). Routers typically include routing protocolsoftware which provide other routers with routes that are available.However, routing protocols vary in the degree of “chattiness” (thenumber and size of messages transmitted to perform the routingprotocol). Generally, routing protocols that require less bandwidth arepreferred. For example, a routing protocol that requires relativelylittle bandwidth (e.g., link state) is preferred over a routing protocolthat requires relatively greater bandwidth (e.g., distance vector).Accordingly, the bandwidth required by the protocol used is significant,particularly if routes do not change, since this creates a large amountof unnecessary traffic.

As described above, the exchanged routing information may specifynetworks associated with the mobile router. At least a portion of theexchanged routing information is then stored in at least one routingtable. By way of example, a routing table associated with the HomeAgent, the mobile router, or both, may be updated to link the networkswith the care-of address for the mobile router.

If it is determined at step 924 that there is no Foreign Agent, theprocess is completed at step 926. Since there is no Foreign Agent, themobile router may tunnel a routing update directly to the Home Agentrather than via the Foreign Agent. As a result, the first mode does notrequire a visitor table. Moreover, recursive tunneling is not requiredbecause routing updates are tunneled directly to the Home Agent.

If it is determined at step 924 that there is a Foreign Agent, a visitortable is updated at the Foreign Agent with an entry for the specifiednetworks such that the mobile router is associated with the identifiednetworks. The process is completed at step 930.

Installing routes to mobile networks via normal IP routing protocolsprovides numerous advantages. This implementation is scalable for manyfixed nodes on networks associated with a mobile router since networksrather than specific hosts are included in the appropriate tables.Moreover, a mapping table is not required. As a result, when the statusof associated networks changes, tables may be dynamically updated toreflect this information. In addition, the format of the registrationrequest need not be altered as required in the second embodiment.

Although there are certain advantages, this implementation routesprotocol traffic on a wireless link. As a result, in systems wherebandwidth is limited, it may be desirable to chose one of the otherembodiments described herein, or at least choose a routing protocol thatconsumes relatively little bandwidth. Additionally, this method requiresrecursive tunneling (i.e., the third encapsulation step) when a foreignagent is used since the Foreign Agent needs the care-of address toascertain the networks associated with the mobile router. Thus, using acollocated care-of address may sometimes be desirable over using aForeign Agent care-of address.

The present invention provides methods and apparatus permitting a mobilerouter to register with a Home Agent. The above-described embodimentspermit registration via a Foreign Agent care-of address as well as acollocated care-of address. Accordingly, roaming nodes that do not haveMobile IP software, hardware and/or firmware may be provided Mobile IPfunctionality through the use of a mobile router.

The invention can also be embodied as computer readable code on acomputer readable medium. The computer readable medium is any datastorage device that can store data which can thereafter be read by acomputer system. Examples of the computer readable medium includeread-only memory, random-access memory, CD-ROMs, magnetic tape, andoptical data storage devices.

The apparatus (Home Agent, Foreign Agent, and/or mobile router) of thisinvention may be specially constructed for the required purposes, or maybe a general purpose programmable machine selectively activated orreconfigured by a computer program stored in memory. The processespresented herein are not inherently related to any particular router orother apparatus. In a preferred embodiment, any of the Home and ForeignAgents and mobile routers of this invention may be specially configuredrouters such as specially configured router models 2500, 2600, 3600,4000, 4500, 4700, 7200, and 7500 available from Cisco Systems, Inc. ofSan Jose, Calif. A general structure for some of these machines willappear from the description given below.

Referring now to FIG. 10, a router/agent 1002 of the present inventionincludes a master central processing unit (CPU) 1004, low and mediumspeed interfaces 1006, and high speed interfaces 1008. When acting underthe control of appropriate software or firmware, the CPU 1004 isresponsible for such router tasks as routing table computations andnetwork management. It is also responsible for registration, packettunneling and other Mobile IP functions of a Home Agent or a ForeignAgent. It may include one or more microprocessor chips 1010 selectedfrom complex instruction set computer (CISC) chips (such as the MotorolaMPC860 microprocessor or the Motorola 68030 microprocessor, reducedinstruction set computer (RISC) chips, or other available chips). In apreferred embodiment, a memory 1012 (such as non-volatile RAM and/orROM) also forms part of CPU 1004. However, there are many different waysin which memory could be coupled to the system.

The interfaces 1008 and 1006 are typically provided as interface cards.Generally, they control the sending and receipt of data packets over thenetwork and sometimes support other peripherals used with the router1002. The low and medium speed interfaces 1006 include a multiportcommunications interface 1014, a serial communications interface 1016,and a token ring interface 1018. The high speed interfaces 1008 includean FDDI interface 1020 and a multiport ethernet interface 1022.Preferably, each of these interfaces (low/medium and high speed)includes (1) a plurality of ports appropriate for communication with theappropriate media, and (2) an independent processor such as the 2901 bitslice processor (available from Advanced Micro Devices corporation ofSanta Clara Calif.), and in some instances (3) volatile RAM. Theindependent processors control such communications intensive tasks aspacket switching and filtering, and media control and management. Byproviding separate processors for the communications intensive tasks,this architecture permits the master microprocessor 1004 to efficientlyperform routing computations, network diagnostics, security functions,etc.

The low and medium speed interfaces are coupled to the master CPU 1004through a data, control, and address bus 1024. High speed interfaces1008 are connected to the bus 1024 through a fast data, control, andaddress bus 1026 which is in turn connected to a bus controller 1028.The bus controller functions are provided by a processor such as a 2901bit slice processor.

Although the system shown in FIG. 10 is a preferred router of thepresent invention, it is by no means the only router architecture onwhich the present invention can be implemented. For example, anarchitecture having a single processor that handles communications aswell as routing computations, etc. would also be acceptable. Further,other types of interfaces and media could also be used with the router.Still further, in some cases, the invention can be implemented onnetwork devices other than routers.

Although illustrative embodiments and applications of this invention areshown and described herein, many variations and modifications arepossible which remain within the concept, scope, and spirit of theinvention, and these variations would become clear to those of ordinaryskill in the art after perusal of this application. For instance,although the specification has described routers, other entities used totunnel packets to mobile nodes on remote network segments can be used aswell. For example, bridges or other less intelligent packet switches mayalso employ the standby protocol of this invention. Accordingly, thepresent embodiments are to be considered as illustrative and notrestrictive, and the invention is not to be limited to the details givenherein, but may be modified within the scope and equivalents of theappended claims.

1. In a Home Agent, a method for providing Mobile IP mobile routerfunctionality, the method comprising: receiving a registration requestpacket, the registration request packet including a care-of address forthe mobile router; identifying one or more networks associated with themobile router; updating a routing table to associate the identifiednetworks with the care-of address; and updating a mobility binding tableto include the care-of address for the mobile router.
 2. The method asrecited in claim 1, wherein identifying one or more networks comprises:identifying the one or more networks associated with the mobile routerfrom a mapping table associating the mobile router with the networks. 3.The method as recited in claim 1, wherein identifying one or morenetworks comprises: identifying the networks associated with the mobilerouter from the registration request packet.
 4. The method as recited inclaim 3, wherein the registration request packet includes an extensionspecifying the networks linked to the mobile router and a statusassociated with each network, wherein identifying the networksassociated with the mobile router from the registration request packetcomprises: ascertaining each network specified in the extension that hasa status indicating that the network is in an active state.
 5. Themethod as recited in claim 1, wherein the care-of address is an IPaddress of a Foreign Agent.
 6. The method as recited in claim 1, whereinthe care-of address is a collocated care-of address.
 7. The method asrecited in claim 1, wherein the registration request packet includes anextension specifying at least one network linked to and associated witha mobile router.
 8. The method as recited in claim 7, where each networkspecified in the extension is associated with a network status.
 9. Themethod as recited in claim 8, wherein the network status is in a firststate when the network is up, and is otherwise in a second state.
 10. Acomputer-readable medium storing thereon computer-readable instructionsfor providing Mobile IP mobile router functionality in a Home Agent,comprising: instructions for receiving a registration request packet,the registration request packet including a care-of address for themobile router; instructions for identifying one or more networksassociated with the mobile router; instructions for updating a routingtable to associate the identified networks with the care-of address; andinstructions for updating a mobility binding table to include thecare-of address for the mobile router.
 11. The computer-readable mediumas recited in claim 10, wherein the instructions for identifying one ormore networks comprises: instructions for identifying the one or morenetworks associated with the mobile router from a mapping tableassociating the mobile router with the networks.
 12. Thecomputer-readable medium as recited in claim 10, wherein theinstructions for identifying one or more networks comprises:instructions for identifying the networks associated with the mobilerouter from the registration request packet.
 13. The computer-readablemedium as recited in claim 12, wherein the registration request packetincludes an extension specifying the networks linked to the mobilerouter and a status associated with each network, wherein theinstructions for identifying the networks associated with the mobilerouter from the registration request packet comprises: instructions forascertaining each network specified in the extension that has a statusindicating that the network is in an active state.
 14. Thecomputer-readable medium as recited in claim 10, wherein the care-ofaddress is an IP address of a Foreign Agent.
 15. The computer-readablemedium as recited in claim 10, wherein the care-of address is acollocated care-of address.
 16. The computer-readable medium as recitedin claim 10, wherein the registration request packet includes anextension specifying at least one network linked to and associated witha mobile router.
 17. The computer-readable medium as recited in claim16, where each network specified in the extension is associated with anetwork status.
 18. The computer-readable medium as recited in claim 17,wherein the network status is in a first state when the network is up,and is otherwise in a second state.
 19. A Home Agent adapted forproviding Mobile IP mobile router functionality, comprising: aprocessor; and a memory, at least one of the processor and the memorybeing adapted for: receiving a registration request packet, theregistration request packet including a care-of address for the mobilerouter; identifying one or more networks associated with the mobilerouter; updating a routing table to associate the identified networkswith the care-of address; and updating a mobility binding table toinclude the care-of address for the mobile router.
 20. The Home Agent asrecited in claim 19, wherein identifying one or more networks comprises:identifying the one or more networks associated with the mobile routerfrom a mapping table associating the mobile router with the networks.21. The Home Agent as recited in claim 19, wherein identifying one ormore networks comprises: identifying the networks associated with themobile router from the registration request packet.
 22. The Home Agentas recited in claim 21, wherein the registration request packet includesan extension specifying the networks linked to the mobile router and astatus associated with each network, wherein identifying the networksassociated with the mobile router from the registration request packetcomprises: ascertaining each network specified in the extension that hasa status indicating that the network is in an active state.
 23. The HomeAgent as recited in claim 19, wherein the care-of address is an IPaddress of a Foreign Agent.
 24. The Home Agent as recited in claim 19,wherein the care-of address is a collocated care-of address.
 25. TheHome Agent as recited in claim 19, wherein the registration requestpacket includes an extension specifying at least one network linked toand associated with a mobile router.
 26. The Home Agent as recited inclaim 25, where each network specified in the extension is associatedwith a network status.
 27. The Home Agent as recited in claim 26,wherein the network status is in a first state when the network is up,and is otherwise in a second state.
 28. A Home Agent adapted forproviding Mobile IP mobile router functionality, comprising: means forreceiving a registration request packet, the registration request packetincluding a care-of address for the mobile router; means for identifyingone or more networks associated with the mobile router; means forupdating a routing table to associate the identified networks with thecare-of address; and means for updating a mobility binding table toinclude the care-of address for the mobile router.
 29. The Home Agent asrecited in claim 28, wherein the means for identifying one or morenetworks comprises: means for identifying the one or more networksassociated with the mobile router from a mapping table associating themobile router with the networks.
 30. The Home Agent as recited in claim28, wherein the means for identifying one or more networks comprises:means for identifying the networks associated with the mobile routerfrom the registration request packet.
 31. The Home Agent as recited inclaim 30, wherein the registration request packet includes an extensionspecifying the networks linked to the mobile router and a statusassociated with each network, wherein the means for identifying thenetworks associated with the mobile router from the registration requestpacket comprises: means for ascertaining each network specified in theextension that has a status indicating that the network is in an activestate.
 32. The Home Agent as recited in claim 28, wherein the care-ofaddress is an IP address of a Foreign Agent.
 33. The Home Agent asrecited in claim 28, wherein the care-of address is a collocated care-ofaddress.
 34. The Home Agent as recited in claim 28, wherein theregistration request packet includes an extension specifying at leastone network linked to and associated with a mobile router.
 35. The HomeAgent as recited in claim 34, where each network specified in theextension is associated with a network status.
 36. The Home Agent asrecited in claim 35, wherein the network status is in a first state whenthe network is up, and is otherwise in a second state.
 37. In a ForeignAgent supporting Mobile IP a method for use with a mobile router whichregisters with a Home Agent via the Foreign Agent, comprising: receivinga registration request packet including an extension specifying one ormore networks linked to and associated with the mobile router;identifying the one or more networks linked to and associated with themobile router from the registration request packet; and updating a tableto include at least one entry for the one or more networks that arelinked to and associated with the mobile router such that the mobilerouter is associated with the one or more networks.
 38. The method asrecited in claim 37, wherein the one or more networks are eachdesignated by an IP address.
 39. The method as recited in claim 37,wherein the mobile router is designated by an IP address.
 40. The methodas recited in claim 37, wherein the table is a visitor table.
 41. AForeign Agent supporting Mobile IP for use with a mobile router whichregisters with a Home Agent via the Foreign Agent, comprising: means forreceiving a registration request packet including an extensionspecifying one or more networks linked to and associated with the mobilerouter; means for identifying the one or more networks linked to andassociated with the mobile router from the registration request packet;and means for updating a table to include at least one entry for the oneor more networks that are linked to and associated with the mobilerouter such that the mobile router is associated with the one or morenetworks.
 42. The Foreign Agent as recited in claim 41, wherein the oneor more networks are each designated by an IP address.
 43. The ForeignAgent as recited in claim 41, wherein the mobile router is designated byan IP address.
 44. The Foreign Agent as recited in claim 41, wherein thetable is a visitor table.
 45. A Foreign Agent supporting Mobile IP foruse with a mobile router which registers with a Home Agent via theForeign Agent, comprising: a processor; and a memory, at least one ofthe processor and the memory being adapted for: receiving a registrationrequest packet including an extension specifying one or more networkslinked to and associated with the mobile router; identifying the one ormore networks linked to and associated with the mobile router from theregistration request packet; and updating a table to include at leastone entry for the one or more networks that are linked to and associatedwith the mobile router such that the mobile router is associated withthe one or more networks.
 46. The Foreign Agent as recited in claim 45,wherein the one or more networks are each designated by an IP address.47. The Foreign Agent as recited in claim 45, wherein the mobile routeris designated by an IP address.
 48. The Foreign Agent as recited inclaim 45, wherein the table is a visitor table.
 49. A computer-readablemedium storing thereon computer-readable instructions for performing amethod for use with a mobile router which registers with a Home Agentvia a Foreign Agent supporting Mobile IP, comprising: instructions forreceiving a registration request packet including an extensionspecifying one or more networks linked to and associated with the mobilerouter; instructions for identifying the one or more networks linked toand associated with the mobile router from the registration requestpacket; and instructions for updating a table to include at least oneentry for the one or more networks that are linked to and associatedwith the mobile router such that the mobile router is associated withthe one or more networks.
 50. The computer-readable medium as recited inclaim 49, wherein the one or more networks are each designated by an IPaddress.
 51. The computer-readable medium as recited in claim 49,wherein the mobile router is designated by an IP address.
 52. Thecomputer-readable medium as recited in claim 49, wherein the table is avisitor table.
 53. A method for providing Mobile IP mobile routerfunctionality in a Home Agent, the method comprising: receiving aregistration request, the registration request including a care-ofaddress associated with a mobile router and an extension specifying atleast one network linked to the mobile router; identifying one or morenetworks associated with the mobile router from the extension; updatinga routing table to associate the identified networks with the care-ofaddress; and updating a mobility binding table to associate the care-ofaddress with the mobile router.
 54. The method as recited in claim 53,further comprising: updating a visitor table at a Foreign Agent withentries for selected networks that are specified in the extension suchthat the selected networks are associated with the mobile router. 55.The method as recited in claim 53, wherein the extension furtherincludes a status for each network associated with the mobile router,and wherein identifying one or more networks comprises: ascertainingeach network specified in the extension that has a status indicatingthat the network is in an active state.
 56. A computer-readable mediumstoring thereon computer-readable instructions for providing Mobile IPmobile router functionality in a Home Agent, comprising: instructionsfor receiving a registration request, the registration request includinga care-of address associated with a mobile router and an extensionspecifying at least one network linked to the mobile router;instructions for identifying one or more networks associated with themobile router from the extension; instructions for updating a routingtable to associate the identified networks with the care-of address; andinstructions for updating a mobility binding table to associate thecare-of address with the mobile router.
 57. The computer-readable mediumas recited in claim 56, further comprising: instructions for updating avisitor table at a Foreign Agent with entries for selected networks thatare specified in the extension such that the selected networks areassociated with the mobile router.
 58. The computer-readable medium asrecited in claim 56, wherein the extension further includes a status foreach network associated with the mobile router, and wherein theinstructions for identifying one or more networks comprises:instructions for ascertaining each network specified in the extensionthat has a status indicating that the network is in an active state. 59.A Home Agent adapted for providing Mobile IP mobile router functionalityin a Home Agent, comprising: a processor; and a memory, at least one ofthe processor and the memory being adapted for: receiving a registrationrequest, the registration request including a care-of address associatedwith a mobile router and an extension specifying at least one networklinked to the mobile router; identifying one or more networks associatedwith the mobile router from the extension; updating a routing table toassociate the identified networks with the care-of address; and updatinga mobility binding table to associate the care-of address with themobile router.
 60. The Home Agent as recited in claim 59, wherein atleast one of the processor and the memory are further adapted for:updating a visitor table at a Foreign Agent with entries for selectednetworks that are specified in the extension such that the selectednetworks are associated with the mobile router.
 61. The Home Agent asrecited in claim 59, wherein the extension further includes a status foreach network associated with the mobile router, and wherein identifyingone or more networks comprises: ascertaining each network specified inthe extension that has a status indicating that the network is in anactive state.
 62. A Home Agent adapted for providing Mobile IP mobilerouter functionality in a Home Agent, comprising: means for receiving aregistration request, the registration request including a care-ofaddress associated with a mobile router and an extension specifying atleast one network linked to the mobile router; means for identifying oneor more networks associated with the mobile router from the extension;means for updating a routing table to associate the identified networkswith the care-of address; and means for updating a mobility bindingtable to associate the care-of address with the mobile router.
 63. TheHome Agent as recited in claim 62, further comprising: means forupdating a visitor table at a Foreign Agent with entries for selectednetworks that are specified in the extension such that the selectednetworks are associated with the mobile router.
 64. The Home Agent asrecited in claim 62, wherein the extension further includes a status foreach network associated with the mobile router, and wherein the meansfor identifying one or more networks comprises: means for ascertainingeach network specified in the extension that has a status indicatingthat the network is in an active state.
 65. A method for providingMobile IP mobile router functionality, the method comprising: receivinga registration request packet including a care-of address for the mobilerouter; updating a mobility binding table to include the care-of addressfor the mobile router; exchanging routing information between a HomeAgent and a mobile router such that the Home Agent receives informationidentifying one or more networks coupled to the mobile router; andupdating at least one routing table such that the one or more identifiednetworks coupled to the mobile router are associated with the care-ofaddress.
 66. The method as recited in claim 65, further comprising:updating a visitor table at a Foreign Agent with an entry for theidentified networks such that the mobile router is associated with theidentified networks.
 67. The method as recited in claim 66, whereinupdating a visitor table is performed when the care-of address is an IPaddress of a Foreign Agent.
 68. The method as recited in claim 65,wherein updating at least one routing table comprises: storing at leasta portion of the exchanged routing information in a routing tableassociated with the Home Agent.
 69. The method as recited in claim 65,wherein updating at least one routing table comprises: storing at leasta portion of the exchanged routing information in a routing tableassociated with the mobile router.
 70. The method as recited in claim65, wherein exchanging routing information is performed via an IProuting protocol.
 71. A computer-readable medium storing thereoncomputer-readable instructions for providing Mobile IP mobile routerfunctionality, comprising: instructions for receiving a registrationrequest packet including a care-of address for the mobile router;instructions for updating a mobility binding table to include thecare-of address for the mobile router; instructions for exchangingrouting information between a Home Agent and a mobile router such thatthe Home Agent receives information identifying one or more networkscoupled to the mobile router; and instructions for updating at least onerouting table such that the one or more identified networks coupled tothe mobile router are associated with the care-of address.
 72. Thecomputer-readable medium as recited in claim 71, further comprising:instructions for updating a visitor table at a Foreign Agent with anentry for the identified networks such that the mobile router isassociated with the identified networks.
 73. The computer-readablemedium as recited in claim 72, wherein updating a visitor table isperformed when the care-of address is an IP address of a Foreign Agent.74. The computer-readable medium as recited in claim 71, wherein theinstructions for updating at least one routing table comprises:instructions for storing at least a portion of the exchanged routinginformation in a routing table associated with the Home Agent.
 75. Thecomputer-readable medium as recited in claim 71, wherein theinstructions for updating at least one routing table comprises:instructions for storing at least a portion of the exchanged routinginformation in a routing table associated with the mobile router. 76.The computer-readable medium as recited in claim 71, wherein exchangingrouting information is performed via an IP routing protocol.
 77. A HomeAgent adapted for providing Mobile IP mobile router functionality,comprising: a processor; and a memory, at least one of the processor andthe memory being adapted for: receiving a registration request packetincluding a care-of address for the mobile router; updating a mobilitybinding table to include the care-of address for the mobile router;exchanging routing information between a Home Agent and a mobile routersuch that the Home Agent receives information identifying one or morenetworks coupled to the mobile router; and updating at least one routingtable such that the one or more identified networks coupled to themobile router are associated with the care-of address.
 78. The HomeAgent as recited in claim 77, wherein at least one of the processor andthe memory are further adapted for: updating a visitor table at aForeign Agent with an entry for the identified networks such that themobile router is associated with the identified networks.
 79. The HomeAgent as recited in claim 78, wherein updating a visitor table isperformed when the care-of address is an IP address of a Foreign Agent.80. The Home Agent as recited in claim 77, wherein updating at least onerouting table comprises: storing at least a portion of the exchangedrouting information in a routing table associated with the Home Agent.81. The Home Agent as recited in claim 77, wherein updating at least onerouting table comprises: storing at least a portion of the exchangedrouting information in a routing table associated with the mobilerouter.
 82. The Home Agent as recited in claim 77, wherein exchangingrouting information is performed via an IP routing protocol.
 83. A HomeAgent adapted for providing Mobile IP mobile router functionality,comprising: means for receiving a registration request packet includinga care-of address for the mobile router; means for updating a mobilitybinding table to include the care-of address for the mobile router;means for exchanging routing information between a Home Agent and amobile router such that the Home Agent receives information identifyingone or more networks coupled to the mobile router; and means forupdating at least one routing table such that the one or more identifiednetworks coupled to the mobile router are associated with the care-ofaddress.
 84. The Home Agent as recited in claim 83, further comprising:means for updating a visitor table at a Foreign Agent with an entry forthe identified networks such that the mobile router is associated withthe identified networks.
 85. The Home Agent as recited in claim 84,wherein updating a visitor table is performed when the care-of addressis an IP address of a Foreign Agent.
 86. The Home Agent as recited inclaim 83, wherein the means for updating at least one routing tablecomprises: means for storing at least a portion of the exchanged routinginformation in a routing table associated with the Home Agent.
 87. TheHome Agent as recited in claim 83, wherein the means for updating atleast one routing table comprises: means for storing at least a portionof the exchanged routing information in a routing table associated withthe mobile router.
 88. The Home Agent as recited in claim 83, whereinexchanging routing information is performed via an IP routing protocol.